The failure to detect, find and correct membrane defects during and as soon after its installation as possible, can cause premature failure. Problems include design deficiencies, faulty application of the membrane system and damage by subsequent tradesmen. Roof designs incorporating a waterproofing membrane under a green roof, insulation layer, wear-course, or topping slab greatly exacerbate the problem of leak locating. The early detection of leaks in waterproof membranes is crucial during construction and for effective roof maintenance. Leaks in conventional roof assemblies allow moisture to accumulate under the membrane in the underlying components such as protection boards and insulation. Accumulated water in insulation compromises its thermal properties. Accumulated water in construction materials can cause rotting and other damage which is very costly to repair.
Low voltage electrical conductance testing is often used to detect and locate leaks in waterproof membranes. The principle technique of the conductance leak location method is to establish an electrical potential between the electrically insulating membrane and the underlying roof substrate. A controlled surface covering of water forms the conductive path horizontally across the membrane to any membrane breach. At a breach location, the test instrument detects the electrical path that is formed through the water leaking to the conductive substrate below.
Low voltage electrical methods to detect and locate breaches are highly effective; however they require an electrically conductive surface immediately below and in intimate contact with the membrane. Often membranes in conventional assemblies are adhered or mechanically fastened to non-conductive materials such as plywood substrate or protection boards which inhibit electric conductance testing.